Laser diode drive circuit and amplifying circuit for optical disc recording and/or reproducing apparatus

An optical disc recording and/or reproducing apparatus including a laser diode drive circuit, said laser diode drive circuit comprising:

• a plurality of laser diodes for outputting laser beams having different wavelengths;
• a switch circuit for selectively connecting a required laser diode from said plurality of laser diodes;
• a laser diode drive power supply circuit for driving the laser diode selectively connected by said switch circuit;
• a photodiode for detecting at least part of laser beams emitted from said laser diode to convert a detected part of laser beams into an electrical signal;
• a plurality of current-to-voltage conversion amplifiers connected to an output of said photodiode, being capable of adjusting conversion resistance values and having differently designed center conversion resistance values;
• and
• an automatic power control circuit connected to outputs of said current-to-voltage conversion amplifiers to output a feedback signal to said laser diode drive power supply circuit.

A laser diode drive method for an optical disc recording and/or reproducing apparatus, comprising the steps of:

• selectively connecting a laser diode from a plurality of laser diodes having different output wavelengths to a laser diode drive power supply circuit with a first switch circuit;
• driving said laser diode drive power supply circuit to allow the connected laser diode to emit laser beams;
• detecting at least part of laser beams emitted from said laser diode to convert said detected part of laser beams into an electrical signal by a photodiode;
• outputting said electrical signal to a corresponding current-to-voltage conversion amplifier of a plurality of current-to-voltage conversion amplifiers, the corresponding amplifier being capable of adjusting conversion resistance values and having differently designed center conversion resistance values, wherein said electrical signal is current-to-voltage-converted and is amplified;
• selectively connecting an output of a required current-to-voltage conversion amplifier from said plurality of current-to-voltage conversion amplifiers to an automatic power control circuit with a second switch circuit;
• generating a feedback signal from said electrical signal, which has been current-to-voltage-converted and amplified, by said automatic power control circuit;
• and
• outputting said feedback signal to said laser diode drive power supply circuit to effect a closed loop control.